Seal for fluid pumps



May 30, 1950 T. H. HOLMES 2,509,973

SEAL FOR FLUID PUMPS Filed Oct. 2, 1944 INVEN TO'R. TIPENT ill [01.441529 AGENT Patented May 30, 1950 UNITED STATES PATENT OFFICE SEAL FOR FLUID Conn, aim, by Nilec-Bemcnt-Po Coma, a eel-notation Application October 2, 1944, Serial No. 556,700 3 Claims. (Cl. 288-11) This invention relates to fluid pumps and more particularly to fluid pumps of the rotating and radially movable vane type.

Primarily, the invention relates to an improved form of seal for a pump of the above type particularly adapted for supplying liquid fuel to an aircraft engine.

An object of importance of the invention is to provide an improved seal for the fluid being pumped at the driving end of the pump' casing that will maintain a perfect seal when the driving shaft is subjected to an end thrust as well as when the driving shaft is slightly out of alignment with its driving member. A feature of importance of the invention is that a flange is provided on an intermediate portion of the driving shaft resiliently forced into contact with a member supported against rotation within the casing.

Other objects and advantages will be apparent from the specification and claims and from the drawings which illustrate what is now considered to be a preferred embodiment of the invention. In the drawing annexed hereto and forming a part of this specification:

Figure 1 is a fragmentary longitudinal sectional view thru the driving end of a rotary pump provided with the present invention; and

Figure 2 is a similar view showing another form of the invention, in which a double seal is provided.

In its preferred forms the invention may include the following principal parts: First, a easing having a rotating pump impeller therein provided with radially movable blades or vanes; second, a driving shaft for said impeller splined v thereto at one end; third, a flange outstanding from an intermediate portion of said shaft; fourth, a flexibly supported sealing ring secured nonrotatably within the casing and engagingone face of said flange; and fifth, resilient means holding the ring in sealing contact with the adjacent face of said flange.

Referring more in detail to the figures of the drawing and first to the form of the invention shown in Figure 1, it will be seen that a single seal is provided therein at all times and an efiective double seal at other times.

The pump is of the rotary sliding vane type, and includes a rotor it supported by bearings, one of which is shown at 25. The rotor ill turns in a liner 9 having a central axial opening eccentrio with respect to the axis of rotor 9.

At one end of the pump rotor' In is a driving shaft 12 extending thru seal plate i3 which is 2 suitably secured to the pump-casing H. Splines ll at the inner end of the shaft ['2 engage corresponding splines l5 within the pump rotor It. At the outer or free end of the driving shaft H are splines I. by means of which the shaft It may be rotated by any driving means connectedv thereto.

At an intermediate portion of the driving shaft I2 is an integral flange ll, one face of which bears against a wearing ring of bronze or carbon ll pressed in a suitable recess in the seal plate l3. This member l8 forms a fixed abutment against which the flange I! normally engages. Bearing against the opposite face of the flange I1 is a flexibly supported ring 19. As shown; this ring I! is centrally attached to a diaphragm 2a of flexible material by means of a small sleeve 2| pressed over the ring l9 and holding the diaphragm 2| against a shoulder formed on the ring is. At its outer periphery the diaphragm 20 is held between surfaces of the casing II and seal plate I: so that the ring l9 may move axially a.

limited distance within the casing but is nonrotatably supported therein. Disposed between the end face of the bearing 25 and the flexibly supported ring I! is a helical spring 22 normally forcing the ring l9 into contact with the flange I! on the driving shaft l2 and forcing the shaft II, as shown in Figure 1, to the right. By means of spring 22 the flange I! will be maintained in sealing contact with the bearing ring l8 housed within a recessed portion of the sealing plate 13.

Within the sealing plate l3 are one or more drain conduits It for the removal of any fluid that might escape between the flange H and rings ill and I8.

The drain conduits 24 communicate with the recess in which the wearing ring I8 is seated at' a point on the inside of that ring. The drain passages 26 also communicate with the space surrounding the shaft 52 just outside of the wearing ring i6.

When the parts are in the positions shown in v Figure 1, the liquid inside the pump must, in order to escape from the casing along the shaft 12,- pass radially outward between the sealing surfaces of the ring 59 and the flange ll'l. Any liquid passing betweenthese sealing surfaces enters the small space to the left of wearing ring 18. This fluid tends to collect in the bottom of this space and therefore passes into drain passage 24. Fluid cannot pass from the space at the left of wearing ring I 8 back toward the shaft 1 2 without passing between a second pair of sealing surfaces between the flange I I and the ring I8l 3 Although the sealing surfaces between flange ii and ring i8 do not completely seal the two spaces which they separate, since these spaces are connected thru the drain passages 24, nevertheless these sealing surfaces provide a guide for any fluid leaking past the ring I9, and therefore effectively aid in preventing fluid from leaking to the outside of the pump casing along the shaft l2.

If an inwardly directed end thrust is applied to the splined end is of shaft i2, the flange l'i may be separated from the wearing ring i8, but the ring i9 is always maintained in sealing contact with flange l1.

These pumps are commonly used as fuel pumps on aircraft engines, and they are periodically removed from the engines for inspection and repair purposes. The mounting pads for the pumps and the drive shafts for the pumps vary somewhat with different engines, especially if the engines are somewhat worn. Therefore, it is not uncommon to flnd that the mounting of a given pump on a given engine will produce an end thrust on the pump drive shaft. In the sealing mechanism described, such an end thrust may separate one set of sealing surfaces, but it cannot separate the surfaces of ring is and flange l1.

Referring to the form of invention shown in Figure 2 a double seal construction is shown for a pump of the same type as that shown in Figure 1. In this construction the liner 9, pump rotor l and driving shaft l2 may be similar to the corresponding parts shown in Figure 1. The housing 33 and seal plate 3| also are generally similar to the housing H and seal plate l3 shown in Figure 1. These members 30 and 31, however, are somewhat different in details of construction.

Within the seal plate 31 is a flanged ring 32 loosely surrounding the driving shaft l2 and flexibly supported by means of a diaphragm 33. This ring 32 forms a normally flxed abutment against which the flange 35 engages. The ring 32 is secured to the diaphragm 33 by means of a sleeve 34 tightly fitting the sleeve 32 and holding the diaphragm against the flange on the ring. The outer periphery of the diaphragm 33 is retained between adjacent surfaces of the housing 33 and seal plate 3i so that the ring 32 may move axially to the left as seen in Figure 2 but is nonrotatably supported within the casing.

Between the flanged face of the ring 32 and the flange 35 on the intermediate portion of the driving shaft [2 isdisposed a ring or collar 36 preferably of carbon, bronze or other bearing metal forming a bearing and sealing member for the driving shaft l2. To retain this collar 36 in position relative to the shaft i 2 a portion may be counterbored so that its outer portion may fit freely over the outer periphery of the flange 35.

Bearing against the opposite or pump side of the flange 35 is a flexibly supported ring 31 secured to a diaphragm 33 in the same manner as ring 32 by means of a small sleeve 39 fitting tightly over the ring 36. The outer periphery of the diaphragm 38 is pressed firmly between a rubber grommet 43 overlying the end wall of a recessed portion of the casing 30 and a sleeve 42 fitting within the recess. The seal plate 3| when secured in position forces the sleeve 42 against the diaphragm 38. Within the casing 30 are drain passages 43 which, as shown, also extend thru the sleeve 42.

Ring 32 bears against the end wall-of a counterbored portion of the seal plate 3| and a spring 43 forces ring 31, driving shaft l2, bearing collar 38, and ring 32 toward the right. A light spring 4! bears against ring 34 to force the ring 32 to the left in the event spring fails or the shaft I 2 is moved slightly to the left. Normally, however, the spring 40 exerts a stronger force to the right than spring 4| exerts to the left.

In the sealing arrangement shown in Figure 2, when the parts are in the positions shown in the drawing, both the sealing surfaces of ring 31 and ring 32 are maintained in sealing engagement with flange l2 and ring 36 respectively. If an inwardly directed end thrust is applied to the outer end of the shaft l2, the flange 35 moves inwardly with the shaft, thereby pressing more tightly against the seal ring 31. At the same time, the flange 35 tends to separate from the ring 33, and to permit separation of rings 36 and 32. This tendency is overcome, however, by the spring 4| which forces the rings 32 and 3G to follow the movements of the flange 35. Both sets of sealing surfaces are thereby maintained in engagement at all times, regardless of any end thrust which may be applied to shaft l2.

While I have shown and described certain preferred embodiments of my invention, other modifications thereof will readily occur to those skilled in the art, and I therefore intend my in vention to be limited only by the appended claims.

What I claim is:

1. Apparatus for sealing a rotatable and limitedly translatable shaft to a housing thru which it passes, comprising a flange on said shaft, said housing having an opening greater in diameter than said flange to permit insertion of said shaft and flange therethru, a plate for closing said opening, said plate having an aperture smaller than said flange, said flange and plate cooperating to retain said shaft'in said housing with said shaft projecting thru said aperture, a first ring of material of a low coeflicient of friction between said flange and said plate, drain passages in said plate connecting both sides of said ring. a seal ring located on the opposite side of said flange and having a sealing surface facing said flange, a flexible diaphragm having its edges clamped between said plate and said housing and attached at its center to said seal ring for supporting the same, said diaphragm preventing rotation of said seal but permitting longitudinal movements thereof, and a spring retained between said housing and said ring for maintaining said seal ring in engagement with said flange, said spring also being effective to maintain said flange in engagement with said first ring, thereby forming a running seal to direct any fluid leaking past said seal ring into said drain passages, except when an inwardly directed end thrust is applied to said other end of said shaft. whereupon said spring permits separation of said flange from said first ring while maintaining said seal ring in sealing contact with said flange.

2. Apparatus for sealing a rotatable and limitedly translatable shaft to a housing thru which it passes, comprising a flange on said shaft, said housing having an opening greater in diameter than said flange to permit insertion of said shaft and flange therethru, a plate for closing said opening, said plate having an aperture smaller than said flange, said flange and plate cooperating to retain said shaft in said housing with said shaft projecting thru said aperture, a pair of seal rings located on the opposite sides of said flange and having respective sealing surfaces facing said flange, a pair of flexible diaphragms, each said diaphragm having its edges clamped to said housing and attached at its center to one of said seal rings for supporting the same, said diaphragms preventing rotation of said seal rings but permitting longitudinal movements thereof, one of said seal rings lying between said flange and said plate, a first spring retained between said housing and the other of said rings for maintaining said other seal ring in' engagement with said flange, said flange in sealing engagement with said one ring, and said one ring in engagement with said plate, and a second spring weaker than said first spring retained between said one ring and said plate for maintaining said one ring in sealing engagement with said flange upon inward movement of said shaft and flange due to the application of an inwardly directed end thrust on said other end of said shaft.

3. A fluid sealing apparatus comprising: a casing, a rotatable and limitedly translatable and-tiltable shaft housed in said casing without bearing contact therewith, a flange on said shaft, said casing having an opening greater in diameter than said flange for the location of said shaft and flange wholly within said casing, a plate for closing said opening, said plate having an aperture smaller than said flange, said flange and plate cooperating to retain said shaft in said casing with said shaft projecting through said aperture without bearing contact with said plate, a first seal ring of material of a low coefficient of friction between said flange and said plate and forming a running seal with said flange, a second seal ring located on the opposite side of said flange, a flexible diaphragm having its outer edge clamped to said housing and attached near its center to said second seal ring for supporting the same, said diaphragm preventing rotation of said second seal ring but permitting longitudinal movement thereof, a drain passage opening into the space between said first and second seal rings, and a spring retained between said casing and said second seal ring for maintaining said seal ring in engagement with said flange, said spring also being effective to maintain said flange in engagement with said first seal ring, thereby forming a double running seal wherein any fluid leaking past either seal ring drains into said passage.

TRENT H. HOLMES.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS France 1923 

